another issue with healer LB3 is that you dont get those few seconds of invincibility you'd get from a normal Raise/Resurrection.
So in content like t5/t9/t13, if you were bumped by divebombs and died on the shock border of the arena, you'll insta-die after being insta-raised by healer LB3...
Giving you another "stack" of weakness after you are raised again...

Also it has some range, i've seen some ppl NOT being raised by healer LB3.
Healers get animation locked for like 5 seconds AFTER the cast ended.

So if in theory an "instant" raise to everyone sounds good... in actual content there are many issues that make it not as good as someone would think it is.